1. Field of the Invention
The present invention relates to a hydrogen manufacturing apparatus for manufacturing high-purity hydrogen by reformed natural gas, methanol, or other hydrocarbon.
2. Related Background Art
The pressure swing adsorption (PSA) has been an industrially predominant prior art for refining hydrogen with high purity from a hydrogen-rich gas which has been obtained by steam-reformed natural gas. According to PSA, the pressure of a hydrogen-rich gas which has been introduced in an absorption tower or pressure vessel is changed to repeat the adsorption and desorption to and from an adsorbent so as to separate and refine a target gas. As the adsorbent, for example, a carbon molecular sieve, synthetic zeolite, or the like is used according to the gas to be separated; the target gas is separated by making use of the fact that the properties of the gases adsorbed to those adsorbents are different. The PSA is characterized in that the adsorption per unit adsorbent increases as the pressure is increased, while it decreases as the pressure is decreased.
To manufacture hydrogen using the aforesaid PSA, however, it is required to install three or four absorption towers or pressure vessels when using, for example, an installation capable of producing hydrogen at 600 Nm3/hr. In addition, a dispensing tank must be installed. Hence, the entire arrangement has inevitably become large, preventing compact equipment for producing hydrogen at lower cost from being achieved. For this reason, it has been difficult to install a hydrogen manufacturing apparatus for a system using hydrogen as the fuel (e.g. a motorcar) in a limited space.